This invention relates to a brake system for a vehicle train comprising a tractor and a trailer wherein the trailer has a brake sub-system, hereinafter referred to as being of the kind specified, comprising a pressure transducer on the trailer responsive to a fluid pressure brake demand signal supplied thereto to provide an electrical brake demand signal, an electronic control means on the trailer responsive to the electrical brake demand signal to provide an electrical brake operating signal, and brake valve means on the trailer, responsive to the electrical brake operating signal supplied to the brake valve means by the electronic control means to supply fluid to an actuator to operate a trailer brake under a brake pressure, from a primary source, determined in accordance with the electrical brake operating signal.
Hitherto such a system has been applied to a vehicle train comprising a tractor and a single trailer in which case the fluid pressure brake demand signal is supplied from the tractor to the pressure transducer on the trailer along a relatively short supply line. (GB-2-,131,508)